Vena cava

vena cava, in air-breathing vertebrates, including humans, either of two major trunks, the anterior and posterior venae cavae, that deliver oxygen-depleted blood to the right side of the heart. The anterior vena cava, also known as the precava, drains the head end of the body, while the posterior vena cava, or postcava, drains the tail, or rear, end. In humans these veins are respectively called the superior and inferior venae cavae. Whereas many mammals, including humans, have only one anterior vena cava, other animals have two.